1. Field of the Invention
The present invention relates to an image recording apparatus for recording data such as images, characters, etc. onto a recording medium by using a recording laser and, more particularly, technology of recording data by stabilizing a laser light.
2. Description of the Related Art
In the image recording apparatus which has a laser light source (LD) and forms the images by irradiating the recording laser light emitted from the LD onto the recording medium, when the image data are input, the LD must output a predetermined power even in its standby state where the recording operation is not carried out for a moment after the power supply is turned on. In order to output the predetermined power from the LD, a current which corresponds to the predetermined power must be supplied. At that time, sometimes the desired power cannot be obtained even if a predetermined constant current is supplied to the LD. This is because the LD has the inherent characteristic such that it has a relatively high output when the temperature of the LD is low but it has a relatively low output when the temperature of the LD is high.
Because of this characteristic, the laser light which mates with the image data is output from the LID and at the same the heat is generated when the image data are input into the LD. Since this heat increases the temperature of the LD, the power of the laser to respond to the input current is changed.
For this reason, normally the image recording apparatus heats/cools the LD by using the Peltier element, etc. to control the temperature of the LD such that the LD can be always set at a predetermined temperature (e.g., the steady recording temperature of 25xc2x0 C.) by the temperature controller in order to keep the output characteristic of the LD constant.
However, the temperature controller causes following problems. That is, in the standby state where the power supply of the image recording apparatus is turned on, normally the laser light is not output from the LD and also the temperature control is performed by heating/cooling the LD so as to maintain the LD at the steady recording temperature by using the temperature controller. At this time, if the image data are input abruptly into the LD, the LD generates the heat due to the laser light output and thus the LD itself is heated. Then, the temperature controller cools the LD so as to shift the LD from the increased temperature to the steady recording temperature. Therefore, the temperature of the LD is decreased, but such temperature is lowered excessively low rather than the steady recording temperature as the case may be. Then, the temperature controller heats the LD so as to shift the LD from the excessively low temperature to the steady recording temperature. Finally, the temperature of the LD can be converged to the steady recording temperature after the repetition of above steps, nevertheless the output characteristic of the laser is changed each time when the temperature is changed to come up to the convergence. As the result of this, irregularity of the recorded images is caused, or a thickness of the recorded line is changed, or the light emitting position is changed.
Meanwhile, in case the recording is made onto the transfer type recording medium in the heat mode by using the recording laser, the sensitivity is degraded in three to five figures rather than the case where the recording is made onto the photographic film, the lith film, etc. Therefore, the high output recording laser is employed as the light source. In this case, the output characteristic of the LD is largely changed because such high output recording laser has a large heating value, and thus a possibility to reduce extremely the picture quality is increased higher.
The present invention has been made in view of such circumstance, and it is an object of the present invention to provide an image recording apparatus which can set the recording laser to its stable output state and record the data immediately after the recording is started and can prevent generation of irregularity of the images, unevenness of the line width, the change in the light emitting position, etc.
In order to overcome the above object, an image recording apparatus set forth in claim 1 of the present invention, for recording data of images and characters on a recording medium by using a recording laser, comprising an optical shutter provided in a middle of an optical path of the recording laser to pass or shut off a laser light; and a controller for controlling to close the optical shutter and also output a recording laser light at a predetermined output rate before a data recording operation onto the recording medium, then to interrupt an output of the recording laser and open the optical shutter immediately before recording start of the data, and then start recording of the data.
According to the image recording apparatus, the optical shutter provided in the middle of the optical path of the recording laser is closed and also the recording laser is caused to output the laser light at the predetermined output rate before the data such as the images and the characters are recorded, and the temperature of the recording laser (LD) can be set to the thermal loading state, which is substantially equal to the steady recording state, prior to the recording start. Then, the output of the recording laser is turned off and also the optical shutter is opened immediately before the recording start, and then the recording is started by outputting the recording laser light to coincide with the image data. Therefore, the LD can start the image recording from the temperature which is close to the steady recording state at the time of the recording start and also an amount of change in the temperature of the LD can be reduced. Accordingly, the image recording can be achieved in the stabilized output state of the LD and the input/output characteristic of the LD, and therefore the high quality image recording can be attained.
Preferably, the predetermined output rate is an output rate which mates with a pulse signal generated at a predetermined duty ratio.
According to the image recording apparatus, if the data are recorded on the recording medium which is formed of the binary photosensitive material, the output of the LD can be properly controlled by employing the pulse signal which repeats ON/OFF at predetermined constant intervals.
Preferably, the predetermined output rate is an output rate which mates with a continuous signal having a predetermined intensity level.
According to the image recording apparatus, if the data are recorded on the recording medium which is formed of density gradation recording material, the output of the LD can be properly controlled by employing the continuous signal having the predetermined intensity level.
A first aspect of the apparatus is an image recording apparatus for recording data of images and characters on a recording medium by using a recording laser, comprising:
an optical shutter provided in a middle of an optical path of the recording laser to pass or shut off a laser light; and
a controller for controlling to close the optical shutter and also controlling to drive a recording laser light at a constant laser output rate so as to pre- heat the recording laser before a data recording operation onto the recording medium, then controlling to interrupt an output of the recording laser and open the optical shutter before recording start of the data, and then start recording of the data by driving the recording laser.
A second aspect of the apparatus is an image recording apparatus according to the first aspect, wherein the controller control the recording laser to be driven immediately before recording start of the data.
A third aspect of the apparatus is an image recording apparatus according to the first aspect, wherein the output rate is an output rate which mates with a pulse signal generated at a constant duty ratio.
A fourth aspect of the apparatus is an image recording apparatus according to the first aspect, wherein the output rate is an output rate which mates with a pulse signal generated at a constant duty ratio determined so that the recording laser is heated itself up to a temperature of the recording laser on recording step.
A fifth aspect of the apparatus is an image recording apparatus according to the first aspect, wherein the output rate is an output rate which mates with a continuous signal having a constant intensity level.
A sixth aspect of the apparatus is an image recording apparatus according to the first aspect, wherein the output rate is an output rate which mates with a continuous signal having a constant intensity level determined so that the recording laser is heated itself up to a temperature of the recording laser on recording step.
A seventh aspect of the apparatus is an image recording apparatus according to the first aspect, wherein the controller control the recording laser to be driven to start preheating and preparing for recording, at the same time when a recording signal is input.
An eight aspect of the apparatus is an image recording apparatus according to the first aspect, wherein the controller opens the shutter and drives the recording laser to put into a recording mode, at a time when the pulse signal is low level.
A ninth aspect of the apparatus is an image recording apparatus according to the eighth aspect, wherein the pulse signal has a duty ratio of 50%.
A tenth aspect of the apparatus is an image recording apparatus according to the first aspect, wherein the recording laser can change an output level intensity and can be controlled to multi-tone recording